For a right turn, a left turn or a lane change, a driver of an automobile pivots a turn lever counterclockwise (left turn indication pivoting direction) or clockwise (right turn indication pivoting direction) to indicate a turning direction of the automobile and pivots a steering wheel from a neutral position to a turning direction.
Then, when the automobile finishes turning right, turning right, or changing the lane, the driver pivots the steering wheel in the opposite direction to the above-mentioned pivoting operation to return the steering wheel to the neutral position. Recently, automobiles are structured to automatically return the turn lever to the neutral position along with the driver's pivoting operation of returning the steering wheel to the neutral position.
This is realized by, for example, as shown in FIG. 7 and FIG. 8 (or Patent Document 1), a cancel mechanism 1′ including a turn lever 40 described above, a cancel cam structure 10′, a bracket 30, and a ratchet 20.
The cancel cam structure 10′ is pivoted like a steering wheel (not shown) by an operation of pivoting the steering wheel. The bracket 30 is located between the turn lever 40 and the cancel cam structure 10′, and is pivotable by the pivoting of the cancel cam structure 10′ and the turn lever 40. The ratchet 20 transmits a pivoting force of the cancel cam structure 10′, generated when the steering wheel is pivoted and returned to a neutral position N, to the bracket 30 and thus pivots and returns the bracket 30 and the turn lever 40 to the neutral position N.
This will be described in more detail. In a state where the turn lever 40 and the bracket 30 are at the neutral position N as shown in FIG. 7, the ratchet 20 is urged toward the cancel cam structure 10′ by a ratchet spring 22 forming urging means.
In this state, a non-cancel cam-side end 25 of the ratchet 20, which is on the opposite side to the cancel cam structure 10′, is located between two engaging sections 32 and 33 provided on the bracket 30 for cancelling. The bracket 30 is held at the neutral position N by moderation means (not shown).
From this state, the driver pivots the turn lever 40 as shown in FIG. 8. When the turn lever 40 and the bracket 30 are pivoted to, for example, a left turn indication position L, an urging force of the ratchet spring 22 puts a cancel cam-side end 24 of the ratchet 20 into contact with a cam section 12′ in the cancel cam structure 10′.
At this point, the non-cancel cam-side end 25 of the ratchet 20 approaches the engaging section 32 among the two engaging sections 32 and 33. Along with the pivoting of the bracket 30, a turn signal switch is actuated to blink a turn signal lamp for left turn.
When, in this left turn indication state, the driver pivots the steering wheel leftward (forward direction), which is the same as the direction indicated by the turn lever 40, to pivot the cancel cam structure 10′ leftward, the cam section 12′ of the cancel cam structure 10′ contacts the cancel cam-side end 24 of the ratchet 20 from one side to swing the ratchet 20 with a ratchet shaft 21 being the swinging center.
In this case, the ratchet 20 is pivoted in a direction away from the engaging section 32 approached by the non-cancel cam-side end 25. Therefore, the bracket 30 and the turn lever 40 are kept at the left turn indication position L. During such forward-direction pivoting, the turn signal switch is kept actuated and thus the turn signal lamp for left turn is kept blinking.
By contrast, when, in the above-described left turn indication state, the driver pivots the steering wheel rightward, which is opposite to the direction indicated by the turn lever 40, to pivot the cancel cam structure 10′ rightward, the cam section 12′ of the cancel cam structure 10′ contacts the cancel cam-side end 24 of the ratchet 20 from the opposite side to the above to pivot the ratchet 20 in the opposite direction to the above.
In this case, the ratchet 20 is pivoted in a direction toward the engaging section 32 approached by the non-cancel cam-side end 25. Therefore, the bracket 30, and thus the turn lever 40, are pivoted from the left turn indication position L toward the neutral position N and thus return to the neutral position N. Along with this, the turn signal switch (not shown) is turned off and the turn signal lamp for left turn (not shown) is put out.
The above description is regarding the case where the bracket 30 is pivoted to the left turn indication position L. In the case where the bracket 30 is pivoted to a right turn indication position R, the basic operation is substantially the same except that the pivoting direction of each member is opposite.
The cam section 12′ of the conventional cancel cam structure 10′ is formed of a plastic material. For example, as shown in FIG. 9, the cam section 12′ is arc-shaped and is enclosed by an arc-shaped outer circumferential cam wall 13a′ contactable with the cancel cam-side end 24 of the ratchet 20, an arc-shaped inner wall 13b′ having the same central axis as that of the outer circumferential cam wall 13a′ but having a smaller diameter than that of the outer circumferential cam wall 13a′, and two coupling cam walls 13c′ and 13d′ extending in a radial direction. The inside of the cam section 12′ is hollow (enclosed space S′).
With such a structure of the cam section 12′ of the cancel cam structure 10′, when the turn lever is pivoted to the left turn indication position L (or right turn indication position R) and thus the cancel cam-side end 24 contacts the cam section 12′, there is a problem that noise of contact (hammering noise) of the cam section 12′ of the cancel cam structure 10′ and the cancel cam-side end 24 of the ratchet 20 is large, which disturbs the driver's ears.